My project is to be re-titled, "Conceptual Background of Eighteenth Century Medicine." In it, I study in depth certain aspects crucial for the understanding of medicine in the eighteenth century. These include the decline of Galenism and the rise of the mechanical philosophy; the analysis of the "substantial form," the decline of this concept and yet its persistence in various modalities; the concept of "principles" and "elements" and the similarities and differences in iatrochemistry and iatromechanism; the concept of "nature"; the concept of "causation"; the evaluation of evidence and the modes of explanation; the body-mind problem, and the mechanism-vitalism controversy; and the transition to a new type of medicine in the mid-century. Theconcepts are studied in relation to the primary source material from approximately 1660 to 1750.